Design and simulation of broadband nanoantennae at optical frequencies

The authors investigate the spectral, polarisation and emission properties of a dual-arm spiral nanoantenna and its complementary structure in optical frequency range numerically using finite integration technique. The nanoantenna can enhance the intensity of incident light by orders of magnitude and maintain its emission properties over wide frequency range. They can receive waves of any linear polarisation. The emitted radiation from the antennae is bidirectional and circularly polarised. The distinctive spectral and polarisation properties of the spiral nanoantenna might achieve new landmarks in the field of nanophotonics. To the author´s knowledge this is the first theoretical investigation of a broadband nanoantenna in optical frequency range.